Eye contact is a major form of nonverbal communication and plays a crucial role in our everyday social interactions. While a person may have a difficult time determining the exact angle at which someone else is looking (e.g., a gaze direction), the person can determine whether another person is looking at him and interact with other people via eye contact. Similarly, a device can implement powerful human-object interfaces if it can sense a user's attention via eye contact (e.g., determining whether a user is looking at it). Unfortunately, conventional approaches do not provide mechanisms for directly sensing eye contact.